Refactor: remove SetDisplayWorkAreaInsets calls.

ash/aura/wm_root_window_controller_aura.h

Index: ash/aura/wm_root_window_controller_aura.h
diff --git a/ash/aura/wm_root_window_controller_aura.h b/ash/aura/wm_root_window_controller_aura.h
index 6c82986348b01eda679e5aaec94b608f15c3b8ed..680f2793d95997d441a7cf22324712a79fe84355 100644
--- a/ash/aura/wm_root_window_controller_aura.h
+++ b/ash/aura/wm_root_window_controller_aura.h
@@ -10,6 +10,7 @@
 #include "ash/common/wm_root_window_controller.h"
 #include "base/macros.h"
 #include "base/observer_list.h"
+#include "ui/display/display_observer.h"
 
 namespace aura {
 class Window;
@@ -20,7 +21,8 @@ namespace ash {
 class RootWindowController;
 
 class ASH_EXPORT WmRootWindowControllerAura : public WmRootWindowController,
-                                              public ShellObserver {
+                                              public ShellObserver,
+                                              public display::DisplayObserver {
  public:
   explicit WmRootWindowControllerAura(
       RootWindowController* root_window_controller);
@@ -51,11 +53,16 @@ class ASH_EXPORT WmRootWindowControllerAura : public WmRootWindowController,
   void RemoveObserver(WmRootWindowControllerObserver* observer) override;
 
   // ShellObserver:
-  void OnDisplayWorkAreaInsetsChanged() override;
   void OnFullscreenStateChanged(bool is_fullscreen,
                                 WmWindow* root_window) override;
   void OnShelfAlignmentChanged(WmWindow* root_window) override;
 
+  // DisplayObserver:
+  void OnDisplayAdded(const display::Display& display) override;
+  void OnDisplayRemoved(const display::Display& display) override;
+  void OnDisplayMetricsChanged(const display::Display& display,
+                               uint32_t metrics) override;
+
  private:
   RootWindowController* root_window_controller_;
   base::ObserverList<WmRootWindowControllerObserver> observers_;